Rachel Beth Phillipson
Robustness of our plate settler design is defined as the ability of the plate settlers to produce 1 NTU water over a variety of non-ideal conditions. One set of non-ideal conditions was building a floc blanket with underdoses and overdoses of alum to measure performance through effluent turbidity from the tube settler.
Alexander Campbell Duncan, Rachel Beth Philipson
The Plate Settler Spacing team is currently investigating the Floc Roll-Up Phenomenon in the tube settler. By developing a velocity gradient model, we hope to both analytically and experimentally determine the critical velocity floc particles experience when they begin to roll up the settler tube and into the effluent rather than settling back down the tube and into the floc blanket. The critical velocity is determined using a force balance for a floc particle. In addition to determining this critical velocity, we hope to understand how properties of the flocs themselves affect floc roll-up.
Christine Lauren Catudal, Matthew William Hurst
This experiment explored the impact of water supersaturated with respect to atmospheric pressure on floc blanket formation and performance. This experiment involved collaboration with the Floating Floc Research Team, who supplied the saturated water that served as the influent water to the process.
Miguel Castellanos, John Lopez
The floc hopper probe team aims to create a fully functional floc hopper probe design for future visits to Honduras and elsewhere. Currently, very little information is know about the location or condition of the floc blanket in the floc hopper. This year’s research should lead to a better understanding of the events preceding sedimentation as well as more details on the location of the floc blanket inside the hopper. An experimental setup was created to test different floc hopper probe designs and observe which one gave accurate readings. This year’s team contributions include: a final design of the floc hopper probe and an assembling manual for the current probe design. The team has tackled the problem in the lab and now field testing is required for further improvement of design.
Mallika Bariya, Tanvi Naidu, Chae Young (Flora) Eun
The Fall 2015 Flocculator Efficiency subteam worked on designing, developing, and testing a flocculator model that optimizes the verticalflow flocculator used in AguaClara water treatment plants. The team addressed the accumulation of lowshear regions of water above the top of the lower flocculator baffles, a phenomenon that creates a “dead” region in which collision potential for the creation of flocs is very low. Dead zone formation occurs due to a decrease in fluid velocity as water transitions from the bottom of the flocculator to the top and as it flows over the lower baffles. The team hypothesized that compressing the water flow would increase the fluid velocity and, as a result, allow the water to flow at a higher trajectory over the lower baffles and reduce the formation of dead spaces. Furthermore, the addition of an extra contraction and expansion would create more turbulence in the region above the lower baffle and increase collision potential. This issue was addressed by installing obstacles in the form of slit pipes at the tops of the lower baffles. Test results with these features showed that the obstacles were able to compress the flow and consequently increase the fluid velocity and turbulence in the ‘dead zone’ region. The team measured and observed the results of this design feature by testing the model through flow visualizations using a red dye tracer. Among the variables tested, the best desired effect was observed with a restriction of 78% of channel width, for both laminar flow and potentially turbulent flow (Re= 3000). With a 60% restriction, the formation of a circulating region was observed, although this eventually cleared up. There is a need for further research on how the geometry of the obstacle might be impacting this phenomenon.
Steve Love and Garret Jancich
The Fabrication Team’s purpose is to address current issues or areas of improvement in AguaClara plants. This semester, the team’s tasks included designing and fabricating a probe for monitoring sludge accumulation in the floc hopper. The floc hopper probe team created an operational tool for peering into the floc hopper in order to know when to drain it. The team also began work for developing the research capabilities of the probe. This would be achieved by taking image data via borescope snake camera and translating it into meaningful turbidity/DOM readings.
Alexandra Green, Tiago Viegas, Paul Vieselmeyer
The visualization of the floc blanket in Aguaclara plants has been difficult and limited, so our team has tried to simulate it and create a new apparatus to solve or at least to reduce the problem. We found reports and materials from the turbidimeter team that could help in our task. Research was done on commercial sensors that could help monitor the floc blanket level, but none of the results were feasible. An experimental set up was also created in order to simulate the floc blanket and clear water interface with no success. Finally, a sludge judge apparatus was created to hopefully help with the observation of the floc blanket in San Nicolas.
Surya Kumar, Larry Ge
The sedimentation tanks at AguaClara sustainable drinking water treatment plants are performing well, but they can perform better. When floc settles it becomes sludge. If there is sludge buildup in a sedimentation tank, a host of problems follow: uneven water flow through the sedimentation tank, impaired performance, anaerobic digestion, and methane production. However, if a sedimentation tank can be designed to prevent any flocs from settling, then the drinking water treatment process will never have to be stopped, and the sedimentation tanks will never have to be cleaned. AguaClara is investigating the creation/use of a “Floc Probe” to better understand floc behavior and achieve this improved tank design. The research tool will be used to survey currently functioning sedimentation tanks in Honduras to identify where sludge is building up. Sonar has been found to be a potential solution. Sonar can detect substances of varying densities as well as record at what depth the substance was found. This technology can therefore distinguish between flocs and sludge, and can also recognize the amount of sludge buildup.
Jacqueline Dokko, Javier Espada Fraile
The countercurrent stacked floc blanket reactor is a system for removing suspended solids or dissolved dyes by coagulating them into larger lumps of particles referred to as flocs using opposing currents to run clean water one way and floc-ridden water the other way. Using two standardized reactors, dye and coagulant concentrations, and flow rates, the team worked towards determining whether multiple reactors in a series is more efficient than a single, long reactor. With the known mechanism and the result of the previous research, this semester’s goal was to intensify dye removal by modifying the design of the reactor, system flow path and flow rates. For the future, the flocculator will be modified to be longer allowing larger flocs to form, increasing efficiency of the system as a whole since the discrepancy in flocculator size prevented comparable performance between the single reactor system and the system of reactors in series.
Surya Kumar, Christine Leu, Amlan Sinha, Cindy Dou
Floc blankets, which are suspended layers of highly concentrated flocs, have the potential of being a more efficient option for removing arsenic, fluoride, and certain dyes in terms of energy and water consumption than currently employed techniques. For floc formation, a coagulant needs to be added to the water, allowing particles to adsorb to each other when they collide. Previous research has shown that the coagulant, polyaluminum chloride (PACl), has properties that allow arsenic, fluoride, and certain dyes to adsorb to its surface. The first iteration of this research used three floc blankets in series with a counter-current flow of contaminated water and flocs. By feeding flocs from the last reactor into the second, and from the second into the first, the PACl’s surface area can be saturated. To test this theory and apparatus, a dye, Remazol Brilliant Blue R (RBBR), was chosen to be the contaminant due to its less toxic nature and visual component. With this apparatus and contaminant, this semester’s goals were to test dye removal efficiency from water with varying concentrations of clay, PACl, and dye. With a 1:1 ratio of PACl to dye, a dye removal efficiency of roughly 80% was achieved. However, the transportation of flocs from the third reactor to the second and first was not sustanaibly achieved.
Oge Anyene, Larry Ge, Yuqi Yu
The Fall 2015 High Rate Sedimentation team aims to design a new sedimentation tank that will allow the tank upflow velocity to be significantly increased (by a factor or 2 to 10), without sacrificing particle removal performance (no increase in effluent turbidity). The motivating factors behind this velocity increase would be to decrease the plan view area of the sedimentation tanks, leading to smaller plants and lower the construction costs and to decrease the overall hydraulic retention time of the plant. One of the primary objectives of the new sedimentation tank will be to maintain a consistent floc blanket (i.e. one that allows for excess floc drainage into a floc hopper) similar to the ones found in current AguaClara plants, even with the increased upflow velocity. In order to achieve this goal our proposed design will feature two sets of plate settlers, one set near the bottom of the tank that will be suspended within the floc blanket, and one above them to capture finer particles. To test the feasibility of such a design, several small-scale experiments will be run in the lab. Such experiments will prove to demonstrate whether or not it is possible to maintain a fluidize bed within plate settlers and what the bulk flow of flocs will look like for a floc blanket maintained within plate settlers.
Miguel Castellanos
The floc hopper probe is a devise that is meant to locate the height of the sludge blanket in the floc hopper of AguaClara water treatment plants. Teams in the past have conducted research and eventually fabricated a working probe prototype that was transported down to Honduras in January 2016. The probe was tested at different treatment plants in Honduras and showed promising results with minor complications. This semester, one of the main objectives is to re-size the probe in order to ensure that it is able to enter the PVC pipe port that is in the sedimentation tank channel system. Furthermore, the team will look into making the design more professional while keeping it cost effective.
Note: The final report for this subteam for this semester was not available and the final presentation is linked instead.
Christian Rodriguez, Anthony Verghese, Deniz Yilmazer
Turbidity measurements provide the primary source of performance monitoring at many water treatment plants. However, turbidity readings of floc suspensions do not provide any insight into the performance of subsequent treatment processes. The Floc Size and Count App team’s aim is to create and easy-to-use personal computer application that could measure floc size distribution using a digital camera with appropriate magnification. The app will be written in LabVIEW. The aim for this semester is to develop coding expertise in the LabVIEW environment and start working on the app that will be used in the AguaClara labs and eventually in AguaClara drinking water treatment plants.
Christian Rodrigues, Anthony Verghese, Deniz Yilmazer
Turbidity measurements provide the primary source of performance monitoring at many water treatment plants. Turbidity provides an excellent way to measure overall plant performance, but it does not provide insight into why the water treatment plants are performing well or poorly. The floc size and count app team’s aim is to create and easy-to-use desktop application that would measure floc size distribution and potentially provide insight as to why a plant is performing well or not. The app will be written in LabVIEW and made available for easy use as a stand alone executable application. The aim for this semester is for the team members to finish the LabVIEW program, integrate the program with a camera system, and have other teams test the camera system and software. By the end of the semester, we hope to have a functional prototype than can be tested by other AguaClara Teams in their experiments.
Cheer Tsang, Yeonjin Yun, Ben Gassaway
The introduction of coagulant into turbid water causes collisions of suspended particles with coagulant nanoparticles, which promotes the growth of flocs. However, a large portion of the coagulant dose adheres to pipe walls rather than influent particles, requiring a higher than necessary coagulant dose to account for this effect. In order to minimize coagulant waste, an apparatus called the contact chamber was fabricated to increase collisions between influent particles and coagulant. The Fall 2017 Contact Chamber team analyzed the performance of the contact chamber by comparing influent and effluent turbidity in experiments with and without a contact chamber. After several trials, it was concluded that the contact chamber did not improve the effluent turbidity. In fact, the effluent turbidity with the contact chamber was significantly greater than the effluent turbidity without the contact chamber.
Roswell Lo, Tanvi Naidu, Luna Oiwa
The High G Flocculation team this semester designed an experimental set-up to test the effects of velocity gradient (G) in a flocculator and to determine the optimal G value based on flocculator performance in terms of effluent turbidity. The G value was varied in different trials by varying flocculator flow rate while controlling for coagulant dosage, influent turbidity, flocculation tube length, and upflow velocity through the sedimentation tank. G_theta was kept constant as around 20,000. The constant sedimentation tank upflow velocity was achieved using a waste stream between the flocculator outlet and sedimentation tank. It was found that for a standard coagulant dose, lower G values were associated with lower effluent turbidity, with 100 Hz being the lowest value tested. The same general relationship was observed for a higher coagulant dose, except that the lowest G values resulted in higher effluent turbidity due to floc blanket collapse. Data from this study will be used in the future to inform the geometry of the flocculator, i.e. the optimal distance between baffles in a full-scale water treatment plant.
